The steady increase in capacity and types of digital media devices has driven a need for more sophisticated and flexible digital media interchange protocols and services. Users for instance often wish to share or exchange digital content such as digital photographs, digital videos and other media or content, as well as manipulate and manage the content which they possess. In a typical scenario a user may wish to view the set of videos, photographs, songs or other media on their portable media or other device.
As illustrated in FIG. 1, when a user for example wishes to retrieve or upload a set of digital videos stored on their digital camcorder, they may access a directory on that device to identify the videos which are stored and can be accessed. The digital video content is generally stored in an object-based format, in which each complete video shoot is contained in a media object which has a set of associated attributes or properties, such as length of video, the codec used in that video, date and time information, author or owner information, or other data or properties. The video frames themselves may be stored in a binary format encoding pixel values and other information. In general the binary media object is stored as a single, monolithic data structure with no constituent parts. Rather, the object's properties may identify the frame length, frame size, color depth and other properties needed to read or consume that content. In general object-based storage may make retrieval of media objects, or data synchronization between two or more media devices, more efficient.
When a user wishes to view a list of the media objects stored on their digital camcorder, camera or other device, for example on a connected personal computer or other client, they may be presented with a list of the video objects, along with date and other properties. However, a table or listing of the content by name or other field may not prompt the user with an idea of the content which each video or other object may contain. Identifying content may become even more difficult when for example when the digital device contains a large quantity of media objects. The user however would often like to be given an indication of the content of a given object, for example before printing, storing or otherwise manipulating that content. With some of that objective in mind, some file or media formats permit for example the generation of a thumbnail representation of a digital photograph.
However, audio, video or other media content can often not be readily represented in sample form, and that content is typically not structured for purposes of sample selection. One issue is that a representative sample must be identified by type before it is accessed. The sample must be given a media type to permit an appropriate decoder to be applied, for instance, before showing or playing that sample object to the user via a user interface. Without an indication of a type for the binary sample, deciphering that content for sample purposes is not possible.
Moreover, even with an identified type, for instance indicating a video sample, the permitted ranges of properties for that sample must likewise be defined to permit playback. For example, the pixel size of a video frame or the frame playback rate may need to be constrained within the playback capabilities of a portable device or other playback machine. Even if for example the first five seconds of the content were for instance selected as a default sample, the format, size or other properties of that sample might not be compatible with the portable device or other playback client, so that reliable playback might not be ensured or possible.
The first few frames of a video clip or first few seconds of digital audio may also in many cases not be very representative of the media content as a whole, since video and audio media may vary substantially over the length of the content. Other problems in digital media storage and management exist.